Recent years have witnessed widespread use of millimeter wave (mm-Wave) radars for advanced driver assistance system (ADAS) applications. Compared with other sensing modalities such as a camera, radar has the ability to perform equally well during different times of the day and can be deployed out of sight behind the car bumper or the doors. In many ADAS applications such as parking, cruise control, and braking, the radar is primarily used to find the three-dimensional location of objects around the vehicle. This includes range, azimuth angle, and elevation angle. The range is computed from the round trip delay of the transmitted signal and the two-dimensional (2D) angle is estimated by using the data collected by an antenna array employing a beamforming-based or an eigen-decomposition based high-resolution frequency estimation method.
The use of radar sensors in automotive pedestrian recognition systems is of special interest since radar sensors are less influenced by environmental conditions (e.g. fog, rain, etc.) as other systems like video cameras. Moreover, high resolution radar sensors are available in many modern vehicles as a part of Adaptive Cruise Control (ACC) systems.